1. Field of the Invention
The present invention relates to a magnetic recording element and magnetic recording device and, more particularly, to a magnetic recording element capable of executing a write by supplying a spin-polarized electron, and a magnetic recording device using the same.
2. Description of the Related Art
To control the magnetization direction of a magnetic material, a method of applying a magnetic field has conventionally been employed. In, e.g., a hard disk drive, the magnetization direction of the medium is reversed by a magnetic field generated from the recording head, thereby executing a write. In a solid-state magnetic recording device (MRAM: Magnetic Random Access Memory), a current magnetic field generated by supplying a current to a wiring line arranged near a magnetoresistive element is applied to a cell to control its magnetization direction. These magnetization direction control methods (current magnetic field write methods) utilizing an external magnetic field have a long history and are regarded as established techniques.
Along with the recent progress in nanotechnology, magnetic materials can also noticeably be microfabricated. Accordingly, magnetization control must also locally be done on a nanoscale. However, localization is difficult because a magnetic field fundamentally spreads spatially. As the bit or cell size decreases, the problem of “crosstalk” becomes conspicuous. That is, even when a specific bit or cell is selected, and its magnetization direction is controlled, the magnetic field spreads to adjacent bits or cells. If the magnetic field generation source is made small to localize the magnetic field, no sufficient magnetic field can be generated.
Recently, a “current direct driving magnetization reversal phenomenon” which causes magnetization reversal by supplying a current to a magnetic material has been found (e.g., F. J. Albert, et al., Appl. Phy. Lett. 77, 3809 (2000)).
In this “current direct driving magnetization reversal phenomenon”, a current is supplied to a magnetic layer to spin-polarize electrons. The spin-polarized electrons are caused to pass through the target magnetic layer to reverse its magnetization. More specifically, when the angular momentum of the spin-polarized electrons is transmitted to and acts on the angular momentum of the magnetic material whose magnetization is to be reversed, the magnetization direction of the magnetic material is reversed. When this phenomenon is used, the current can be caused to more directly act on a magnetic material on a nanoscale, as compared to the above-described current magnetic field write methods. Hence, recording on a magnetic material with a finer structure is possible.
However, when the “current direct driving magnetization reversal phenomenon” is used, the current necessary for magnetization reversal is large. Accordingly, the element characteristic degrades due to the influence of heat generated by the reversal current, resulting in a problem of reliability. In addition, a reversal current Jc− for switching from parallel to anti-parallel is larger by several times than a reversal current Jc+ for switching from anti-parallel to parallel. To solve the asymmetry of the reversal currents Jc− and Jc+, the reversal current Jc− for switching from parallel to anti-parallel must be small.